It just depends, if you have a tight bore and a M120 spring, you should be fine for a field game. Now I wouldn't bring a G4 to any op if it's stock. I personally own one and it's far from stock and I'm outranging VFC's with a 6.01 TBB, M120 spring, metal bushings and a new piston. The G4s can beat high-grade guns no doubt if you upgrade it right. If your bringing it to an op, than you need some upgrades or it's gonna be unreliable and a short range gun.
Dusty's Loadout,Primary:CA LWRC PSD(Disabled blowback. Prommy 6.03 tbb and G&P Marine stock.)
Sidearm:Toyko Mauri G17 In Flat Dark Earth(Sexy Beast!)
Preacher's Loadout,Primary:KWA SR10 2GX(Prommy 6.01 tbb otherwise stock.)
Sidearm: TM G18C(Stock)
Airsoft Team in Texas.(only the leaders loadouts are showed)